Implement WebContents.downloadImage() on Java side

content/public/android/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/android/rules.gni")
 
 content_jni_gypi_values = exec_script("//build/gypi_to_gn.py",
                                       [ rebase_path("../../content_jni.gypi") ],
                                       "scope",
@@ skipping 179 matching lines @@
     "java/src/org/chromium/content/browser/input/ThreadedInputConnectionProxyView.java",
     "java/src/org/chromium/content/browser/webcontents/WebContentsImpl.java",
     "java/src/org/chromium/content/browser/webcontents/WebContentsObserverProxy.java",
     "java/src/org/chromium/content/common/CleanupReference.java",
     "java/src/org/chromium/content/common/ContentSwitches.java",
     "java/src/org/chromium/content/common/SurfaceWrapper.java",
     "java/src/org/chromium/content_public/browser/AccessibilitySnapshotCallback.java",
     "java/src/org/chromium/content_public/browser/AccessibilitySnapshotNode.java",
     "java/src/org/chromium/content_public/browser/ContentBitmapCallback.java",
     "java/src/org/chromium/content_public/browser/GestureStateListener.java",
+    "java/src/org/chromium/content_public/browser/ImageDownloadCallback.java",
     "java/src/org/chromium/content_public/browser/JavaScriptCallback.java",
     "java/src/org/chromium/content_public/browser/LoadUrlParams.java",
     "java/src/org/chromium/content_public/browser/NavigationController.java",
     "java/src/org/chromium/content_public/browser/NavigationEntry.java",
     "java/src/org/chromium/content_public/browser/NavigationHistory.java",
     "java/src/org/chromium/content_public/browser/WebContents.java",
     "java/src/org/chromium/content_public/browser/WebContentsObserver.java",
     "java/src/org/chromium/content_public/common/MediaMetadata.java",
     "java/src/org/chromium/content_public/common/Referrer.java",
     "java/src/org/chromium/content_public/common/ScreenOrientationConstants.java",
@@ skipping 192 matching lines @@
   java_files = [
     "junit/src/org/chromium/content/browser/input/GamepadMappingsTest.java",
     "junit/src/org/chromium/content/browser/BindingManagerImplTest.java",
   ]
   deps = [
     ":content_java",
     "//base:base_java",
     "//base:base_java_test_support",
   ]
 }